The Meselson-Stahl experiment made clear predictions regarding experimental outcomes if dispersive,conservative,or semiconservative DNA replication was occurring in their Escherichia coli cells.This experiment enables the detection of "new" and "old" DNA by assessing the _______________ of DNA molecules in the cells.
A)intensity of radioactive labeling
B)density
C)charge distribution along the double helix
D)number of mutations
E)size (length)

Question

Quizplus · Accepted Answer

The Meselson-Stahl experiment involved labeling the DNA of E. coli cells with a heavy isotope of nitrogen, allowing the researchers to track the distribution of isotope-labeled DNA in subsequent generations. By performing centrifugation gradient assays, the researchers were able to separate DNA molecules based on their density. Conservative replication would result in two distinct bands of DNA, one consisting entirely of heavy-labeled DNA and the other entirely of light-labeled DNA. Dispersive replication would result in a smear of intermediate-density DNA molecules. Semiconservative replication, the actual mechanism of DNA replication, would result in two bands, one consisting entirely of light-labeled DNA and one consisting of molecules with intermediate densities. Thus, the density of the DNA molecules allowed the researchers to distinguish between the different modes of replication.

The Meselson-Stahl Experiment Made Clear Predictions Regarding Experimental Outcomes If